Technical Field
The invention relates to a positioning apparatus for positioning poultry legs conveyed in a row in a direction of conveyance along a conveying way in a processing position which represents a reference position for processing of the poultry legs, wherein the drumstick and the thigh of the poultry legs are connected to one another by the knee joint and wherein one axial side of the leg, on which the patella is located, determines the front side of the leg, and the other axial side of the leg, on which the hollow of the knee is located, determines the rear side of the leg, comprising                a conveyor device having carriers which are movable along the conveying way in the direction of conveyance and which convey and hold the poultry legs, each with an ankle joint ball held in an associated mentioned carrier, along the entire conveying way of the positioning apparatus, wherein the carriers hold the poultry legs in a suspended position while they are fed into the positioning device,        a bending device having a stationary positioning element extending in a bending conveying section of the conveying way, and a series of co-running positioning elements which each co-run in the direction of conveyance in association with an associated mentioned carrier, wherein a co-running positioning element forms with the stationary positioning element a pair of positioning elements, of which a first positioning element is configured to engage in the hollow of the knee of the poultry leg and a second positioning element is configured to rest against the thigh on the front side of the leg, and wherein in the bending conveying section of the conveying way, the first positioning element and the second positioning element in the pair produce and determine between them a bending angle which corresponds to the angle of the hollow of the knee and which becomes smaller while lifting the poultry leg from the initial suspended position until the mentioned reference position is reached, and results in corresponding bent positions of the poultry leg, wherein the carriers of the conveyor device are so configured that the ankle joint ball in the carrier is able to move in a manner corresponding to the lifting of the poultry leg, and        a reference holding edge extending in the conveying way, on which the poultry leg is held in a defined lifted position, namely in the reference position, in the region of the knee joint.        
The invention relates also to a method for removing, during conveying, the thigh meat from poultry legs conveyed in a row in the direction of conveyance, wherein the poultry leg is positioned by a positioning apparatus by defined lifting and holding of the knee joint, cuts are applied in the poultry leg meat in the region of the knee of the poultry leg down to the bone, and the thigh meat is pushed from the specifically positioned knee joint to the hip joint bone. The drumsticks and thighs of the poultry legs are connected to one another by the knee joint, and the poultry legs are in a suspended arrangement with the ankle joint balls held in a carrying device.
The poultry legs that are positioned are legs which have been separated from a poultry carcass and consist of the thigh and the drumstick.
State of the Art
A device for processing the legs of poultry is known from EP 0 858 740 A1. The device is equipped with a positioning apparatus of the generic type. The bending device therein has a revolving support plate with recesses, in each of which a poultry leg comes to lie in the region of the knee joint, namely between a fixed (stationary) guide rail and a supporting edge which co-runs with the recesses, which forms a positioning element in each recess. The known device requires a circular or carousel-like guide, the support plate being provided on its lower side with orientation means for orienting the thighs substantially radially in relation to the axis of revolution of the support plate. The bending angle of the poultry leg is made smaller by the guide rail, and the poultry leg is lifted for positioning of the supporting edge in the hollow of the knee. Although a cutting point on the knee joint of the poultry leg is reached independently of certain differences in length of the drumstick, cutting can be carried out only with a single cutting means, whereby the poultry leg has to be brought into the special bent position with the radial orientation of the thigh.
An apparatus having a linear conveying way for removing the thighs from poultry legs is known from DE 691 00 902 T2. The poultry legs are suspended by their tarsal joints and positioned by a leg positioning device. This has positioning blocks co-running in a straight direction of conveyance, which cooperate, in the region in which the poultry leg is cut, with a guide strip, which in turn cooperates with a separating device for executing the cut.
DE 600 13 263 T2 (FIGS. 21 to 28) discloses a device in which poultry legs are positioned in a space between a carrier block and a cutting block, wherein a carrying edge is arranged beneath the patella and moves upwards in order to position the knee joint in relation to a cutting blade arranged on each cutting block. Instead of the knee carrier block, an arm can be provided for positioning the patella.
A method of the generic type is known from DE 691 00 902 (FIGS. 4 to 12). A cylindrical control element of a carousel device has a plurality of scraping units. In each scraping unit, which is equipped with two scraping elements, thigh meat is scraped from the thigh bone of a poultry leg which is suspended by its tarsal joint on a rotating suspension plate. In the scraping unit, the poultry leg is bent approximately at a right angle and brought by one of the scraping elements into a reproducible position in which an incision is made at the back of the knee. With the knee joint in an extended position effected by the two scraping elements, an incision is made below the patella. With the aid of a positioning stop, the incision is always made at the same point of the knee joint, and cutting of the patella is prevented. The two scraping elements of the scraping unit are moved towards the hip joint in order to scrape off the thigh meat. In the scraping unit, the thigh meat can be cut away from the thigh bone. The mentioned cuts are made in each scraping unit while the poultry leg is conveyed in its suspended position by the suspension plate. The legs from which the thigh meat has been removed are transferred to a straight conveying way, on which the thigh bone is cut.
It is characteristic of the known apparatuses that the poultry leg, during cutting in the region of the knee joint, is to be positioned and held in an associated specific bent position, the positioning effected during cutting by defined bending of the poultry leg being eliminated when a cut at the knee joint is complete. Such positioning is considered to be particularly suitable for a circular guide or carousel transport. Circular guides or carousel devices impair the conveying speed, and the adaptation of conveying paths to desired spatial regions is made more difficult. Carrying out and maintaining the positioning of the poultry leg knee joint in a specific bent position associated with the position of the cutting means limit considerably the processing possibilities as a result of the cut, which is to be applied along the conveying way at the position of the associated bend with a specially adapted cutting tool. The application of the cut and/or the variety of cuts are impaired.